1. Field of the Invention
The present invention relates to an image reading apparatus applicable to, say, a facsimile, OCR, etc.
2. Description of Prior Art
An image reading apparatus reads information such as characters and figures on a document and converts it to an electric signal. The typical construction of a conventional image reading apparatus is shown in FIG. 1. Referring to FIG. 1, 31 is a document, 32 and 33 are transport rollers connected to a driving source for conveying the document 31, 34 is a fluorescent lamp (light source) for illuminating the document 31 when transmitted to the reading position, and 35 is a back plate facing to the fluorescent lamp 34 with the document 31 therebetween. 361, 362 and 363 are reflection mirrors which lead light reflected from the document 31 to a CCD (charge coupled device) image sensor 38 described later. 37 is a condenser lens through which the light reflected by the mirror 363 passes. 38 is a CCD image sensor which is mounted on a base 39 to receive light reflected from the document 31 and transmitted through the condenser lens 37 for conversion to an electric signal.
According to the prior art as mentioned above, the optical system (comprising the fluorescent lamp 34, the reflection mirrors 361, 362 and 363 and the condenser lens 37) is inevitably complicated in construction and large in size, resulting in a large image reading apparatus. In addition, the set of mirrors 361, 362 and 363 and the condenser lens 37 in the optical system tend to become displaced, affecting the reading performance adversely.